Hydrocarbon conversion catalyst composition and processes therefor and therewith

ABSTRACT

A catalyst composition, a process for producing the composition and a hydrocarbon conversion process for converting a C 9  + aromatic compound to a C 6  to C 8  aromatic hydrocarbon such as a xylene are disclosed. The composition comprises an acid-treated zeolite having impregnated thereon a metal or metal oxide. The composition can be produced by incorporating the metal or metal oxide into the zeolite. The hydrocarbon conversion process comprises contacting a fluid which comprises a C 9  + aromatic compound with the catalyst composition under a condition sufficient to effect the conversion of a C 9  + aromatic compound to a C 6  to C 8  aromatic hydrocarbon.

This application is a division of application Ser. No. 08/907,194 filedon Aug. 6, 1997, now U.S. Pat. No. 5,929,295.

FIELD OF THE INVENTION

This invention relates to a catalyst composition useful for converting aC₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon, to a processfor producing the composition and to a process for using the compositionin a hydrodealkylation process.

BACKGROUND OF THE INVENTION

It is well known to those skilled in the art that aromatic hydrocarbonsare a class of very important industrial chemicals which find a varietyof uses in petrochemical industry. Recent efforts to convert gasoline tomore valuable petrochemical products have therefore focused on thearomatization of gasoline to aromatic hydrocarbons by catalytic crackingin the presence of a catalyst. The aromatic hydrocarbons produced by thearomatization process include C₆ to C₈ hydrocarbons such as benzene,toluene and xylenes (hereinafter collectively referred to as BTX) whichcan be useful feedstocks for producing various organic compounds andpolymers. However, heavier, less useful aromatic compounds are alsoproduced during the aromatization process. It is, therefore, highlydesirable to convert these compounds to the more useful BTX.

Though a number of catalysts have been used in a hydrodealkylation ortransalkylation process, the conversion of a C₉ + aromatic compound andthe selectivity to BTX are generally not as high as one skilled in theart would desire. Furthermore, a catalyst used in the hydrodealkylationor transalkylation of these heavier aromatic compounds is generallydeactivated in a rather short period because of depositions ofcarbonaceous material such as, for example, coke on the surface of thecatalyst.

Accordingly, there is an ever-increasing need to develop a catalyst anda process for converting these heavier and less useful aromaticcompounds (mainly trimethyl- and tetramethylbenzenes) to the morevaluable BTX hydrocarbons while simultaneously suppressing the cokeformation. Such development would also be a significant contribution tothe art and to the economy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a catalyst composition whichcan be used to convert a C₉ + aromatic compound to a C₆ to C₈ aromatichydrocarbon. Also an object of this invention is to provide a processfor producing the catalyst composition. Another object of this inventionis to provide a process which can employ the catalyst composition toconvert C₉ + aromatic compounds to C₆ to C₈ aromatic compounds. Anadvantage of the catalyst composition is that it decreases coke depositsthereon and exhibits high transalkylation activity, satisfactory yieldof xylenes and BTX and good stability. Other objects and advantages willbecome more apparent as this invention is more fully disclosedhereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used as a catalyst for converting a C₉ + aromatic compoundto a C₆ to C₈ aromatic hydrocarbon is provided. The composition cancomprise an acid-treated zeolite having incorporated therein an activitypromoter.

According to a second embodiment of the invention, a process forproducing a composition which can be used as catalyst in a hydrocarbonconversion is provided. The process can comprise (1) optionallycalcining a zeolite to produce a calcined zeolite; (2) contacting azeolite or a calcined zeolite with an acid under a condition sufficientto produce an acid-treated zeolite; (3) contacting the acid-treatedzeolite with an activity promoter precursor selected from the groupconsisting of silicon compounds, phosphorus compounds, boron compounds,magnesium compounds, tin compounds, titanium compounds, zirconiumcompounds, molybdenum compounds, germanium compounds, indium compounds,lanthanum compounds, cesium compounds, and combinations of two or morethereof under a condition sufficient to incorporate the activitypromoter into the zeolite to form a modified zeolite; and (4) calciningthe modified zeolite.

According to a third embodiment of the present invention, a processwhich can be used for converting a C₉ + aromatic compound to a C₆ to C₈aromatics compound is provided which comprises, consists essentially of,or consists of, contacting a fluid which comprises a C₉ + aromaticcompound, optionally in the presence of an inert fluid such as ahydrogen-containing fluid, with a catalyst composition, which is thesame as disclosed above in the first embodiment of the invention, undera condition effective to convert a C₉ + aromatic compound to an aromatichydrocarbon containing 6 to 8 carbon atoms per molecule.

DETAILED DESCRIPTION OF THE INVENTION

According to the first embodiment of the invention, a composition whichcan be used as catalyst in a transalkylation or hydrodealkylationprocess for converting a C₉ + aromatic compound to a C₆ to C₈ aromatichydrocarbon is provided. The composition comprises, consists essentiallyof, or consists of, a zeolite having incorporated therein, preferablyimpregnated thereon, an activity promoter selected from the groupconsisting of silicon, phosphorus, boron, magnesium, tin, titanium,zirconium, molybdenum, germanium, indium, lanthanum, cesium, any oxidethereof, and combinations of two or more thereof wherein the activitypromoter is present in the composition in a coke-suppressing amount, oran activity-enhancing amount to improve the conversion of a C₉ +aromatic compound, when the composition is used in a transalkylationprocess.

According to the first embodiment of the invention, the weight ratio ofthe activity promoter to the acid-treated zeolite can be any ratio solong as the ratio can enhance or improve the conversion of a C₉ +aromatic compound or suppress or reduce the formation or deposition ofcoke on a zeolite catalyst during the transalkylation process forconverting a C₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon.Generally, the ratio can be in the range of from about 0.0001:1 to about1:1, preferably about 0.0005:1 to about 1:1, more preferably about 0.001:1 to about 0.8: 1 and most preferably from 0.005:1 to 0.5:1 foreffective hydrocarbon conversion and coke reduction or suppression.Alternatively, the activity promoter can be present in the catalystcomposition in the range of from about 0.01 to about 50, preferablyabout 0.05 to about 50, more preferably about 0.1 to about 45, and mostpreferably 0.5 to 33 grams per 100 grams of the catalyst composition.The term "acid-treated zeolite" refers to a zeolite which has beencontacted with an acid, as described in the second embodiment of theinvention, before the zeolite is incorported with an activity promoter.

If a combination of two or more activity promoters is employed, theatomic ratio of one promoter to other promoter(s) can be in the range ofabout 0.01:1 to about 10:1, preferably about 0.1:1 to about 8: 1, morepreferably about 0.5:1 to about 5:1, and most preferably 1:1 to 3:1. Thepresently preferred composition is an acid-treated beta zeolite havingimpregnated thereon molybdenum or molybdenum oxide.

According to the present invention, any activity promoter that, ascompared to use of a zeolite only, can effect the increase in theconversion of a C₉ + aromatic compound to a C₆ -C₈ aromatic hydrocarbonor reduction of coke deposition on the zeolite during the conversion ofa C₉ + aromatic compound to a C₆ to C₈ aromatic hydrocarbon, can beemployed. Presently it is preferred that the activity promoter isselected from the group consisting of silicon, phosphorus, boron,magnesium, tin, titanium, zirconium, molybdenum, germanium, indium,lanthanum, cesium, any oxides thereof, and combinations of two or morethereof. The presently most preferred activity promoter is molybdenum ormolybdenum oxide.

The composition can also be characterized by having the followingphysical characteristics: a micropore surface area, as determined by theBET method using nitrogen, in the range of from about 50 to about 1,000,preferably 50 to 500 m² /g; a micropore pore volume in the range of fromabout 0.1 to about 2.0, preferably about 0.1 to about 1.0 ml/g; anaverage micropore pore diameter in the range of from about 0.1 to about500, preferably about 1 to about 200 Å; and a porosity of more thanabout 20%.

Any commercially available zeolites can be employed as a startingmaterial of the process of the second embodiment of the invention.Examples of suitable zeolites include, but are not limited to, thosedisclosed in Kirk-Othmer Encyclopedia of Chemical Technology, thirdedition, volume 15 (John Wiley & Sons, New York, 1991). The presentlypreferred zeolite, as disclosed above, is a beta zeolite.

Any methods known to one skilled in the art for incorporating a compoundor a portion thereof into a zeolite such as, for example, impregnation,ion exchange, or extrusion can be employed for producing the compositionof the present invention. However, it is presently preferred thecomposition be produced by the process disclosed in the secondembodiment of the invention.

According to the second embodiment of the invention, a zeolite,preferably a beta zeolite, can be optionally contacted with one or moresuitable binders in a liquid, preferably aqueous medium, to form azeolite-binder mixture. Any binders known to one skilled in the art foruse with a zeolite are suitable for use herein. Examples of suitablebinder include, but are not limited to, clays such as for example,kaolinite, halloysite, vermiculite, chlorite, attapulgite, smectite,montmorillonite, illite, saconite, sepiolite, palygorskite, andcombinations of two or more thereof; diatomaceous earth; aluminas suchas for example α-alumina and γ-alumina; silicas; alumina-silica;aluminum phosphate; aluminum chlorohydrate; and combinations of two ormore thereof. Because these binders are well known to one skilled in theart, description of which is omitted herein. The weight ratio of azeolite to a binder can be in a wide range and generally in the range offrom about 200:1 to about 0.1:1, preferably 20:1 to 0.1:20.

The zeolite and the binder can be well mixed by any means known to oneskilled in the art such as stirring, blending, kneading, or extrusion,following which the zeolite-binder mixture can be dried in air at atemperature in the range of from about 20 to about 200° C., preferablyabout 25 to about 175° C., and most preferably 25 to 150° C. for about0.5 to about 50 hours, preferably about 1 to about 30 hours, and mostpreferably 1 to 20 hours, preferably under atmospheric pressure.Thereafter, the dried, zeolite-binder mixture can be further calcined,if desired, in air at a temperature in the range of from about 300 to1000° C., preferably about 350 to about 750° C., and most preferably 450to 650° C. for about 1 to about 30 hours to prepare a calcinedzeolite-binder. If a binder is not desired, a zeolite can also becalcined under similar conditions to remove any contaminants, ifpresent.

A zeolite, a calcined zeolite, or a calcined zeolite-binder can betreated with a compound containing an exchangeable ammonium ion toprepare an ammonium-exchanged zeolite. Whether a zeolite is calcined orcontains a binder, the process or treatment in the second embodiment isthe same for each. For the interest of brevity, only a zeolite isdescribed hereinbelow. Examples of suitable ammonium-containingcompounds include, but are not limited to, ammonium sulfate, ammoniumchloride, ammonium nitrate, ammonium bromide, ammonium fluoride, andcombinations of any two or more thereof. Treatment of the zeolitereplaces the original ions such as, for example, alkali or alkalineearth metal ions of the zeolite with predominantly ammonium ions.Techniques for such treatment are well known to one skilled in the artsuch as, for example, ion exchange with the original ions. For example,a zeolite can be contacted with a solution containing a salt of thedesired replacing ion or ions.

Generally, a zeolite can be suspended in an aqueous solution of anammonium compound. The concentration of the zeolite in the aqueoussolution can be in the range of from about 0.01 to about 200, preferablyabout 0.1 to about 150, more preferably about 1 to about 100, and mostpreferably 5 to 75 grams per liter. The amount of the ammonium compoundrequired depends on the amount of the original ion(s) to be exchanged.Upon the preparation of the solution, the solution can be subject to atemperature in the range of from about 30° C. to about 200° C.,preferably about 40° C. to about 150° C., and most preferably 50° C. to125° C. for about 1 to about 100 hours, preferably about 1 to about 50hours, and most preferably 2 to 25 hours depending on desired degrees ofion exchange. The treatment can be carried out under a pressure in therange of from about 1 to about 10 atmospheres (atm), preferably about 1atm or any pressure that can maintain the required temperature.Thereafter, the treated zeolite can be washed with running water for 1to about 60 minutes followed by drying and calcining to produce calcinedzeolite. The drying and calcining processes can be carried outsubstantially the same as those disclosed above for the preparation of acalcined zeolite or zeolite-binder.

Generally, the ammonium-exchanged zeolite becomes hydrogen exchangedupon calcination or high temperature treatment such that a predominantproportion of its exchangeable cations are hydrogen ions. Theabove-described ion exchanges of exchangeable ions in a zeolite is wellknown to one skilled in the art. See, for example, U.S. Pat. No.5,516,956, disclosure of which is incorporated herein by reference.Because the ion exchange procedure is well known, the description ofwhich is omitted herein for the interest of brevity.

According to the second embodiment of the invention, a zeolite in adesired ionic form, regardless whether calcined or containing a binder,can be optionally contacted with steam under a condition sufficient toeffect the formation of steamed zeolite. Generally the steam temperaturecan be in the range of from about 120° C. to about 1500° C., preferablyabout 200° C. to about 1000° C., more preferably 250° C. to 800° C., andmost preferably 350 to 625 ° C. The treatment can be carried out under apressure that can maintain or accommodate the steam temperature in therange of from about atmospheric pressure to about 2,000, preferably toabout 1,500, and most preferably to 1000 psig.

According to the second embodiment of the invention a zeolite, whetherit has been steamed or not, also can be treated with an acid. Generally,any organic acids, inorganic acids, or combinations of any two or morethereof can be used in the process of the present invention so long asthe acid can reduce the aluminum content in the zeolite. The acid canalso be a diluted aqueous acid solution. Examples of suitable acidsinclude, but are not limited to oxalic acid, citric acid, sulfuric acid,hydrochloric acid, nitric acid, phosphoric acid, formic acid, aceticacid, trifluoroacetic acid, trichloroacetic acid, p-toluenesulfonicacid, methanesulfonic acid, partially or fully neutralized acids whereinone or more protons have been replaced with, for example, a metal(preferably an alkali metal) or ammonium ion, and combinations of anytwo or more thereof. Examples of partially or fully neutralized acidsinclude, but are not limited to, sodium bisulfate, sodium dihydrogenphosphate, potassium hydrogen tartarate, ammonium sulfate, ammoniumchloride, ammonium nitrate, and combinations of two or more thereof. Thepresently preferred acid is oxalic acid.

Any methods known to one skilled in the art for treating a solidcatalyst with an acid can be used in the acid treatment of the presentinvention. Generally, a zeolite material can be suspended in an acidsolution. The concentration of the zeolite in the acid solution can bein the range of from about 0.01 to about 500, preferably about 0.1 toabout 400, more preferably about 1 to about 350, and most preferably 5to 300 grams per liter. The amount of acid required is the amount thatcan maintain the solution in acidic pH during the treatment. Generallythe weight ratio of the zeolite to acid can be in the range of fromabout 0.001:1 to about 100:1 depending on the type of acid employed.Preferably the initial pH of the acid solution containing a zeolite isadjusted to lower than about 7, and preferably lower than about 6. Uponthe pH adjustment of the solution, the solution can be subjected to atreatment at a temperature in the range of from about 30° C. to about200° C., preferably about 35° C. to about 150° C., and most preferably40° C. to 120° C. for about 10 minutes to about 30 hours, preferablyabout 20 minutes to about 25 hours, and most preferably 30 minutes to 20hours. The treatment can be carried out under a pressure in the range offrom about 1 to about 10 atmospheres (atm), preferably about 1 atm solong as the desired temperature can be maintained. Thereafter, theacid-treated zeolite material can be washed with running water for 1 toabout 60 minutes followed by drying, at about 50 to about 1000,preferably about 75 to about 750, and most preferably 100 to 650° C. forabout 0.5 to about 15, preferably about 1 to about 12, and mostpreferably 1 to 10 hours, to produce an acid-treated zeolite. Any dryingmethod known to one skilled in the art such as, for example, air drying,heat drying, spray drying, fluidized bed drying, or combinations of twoor more thereof can be used.

The dried, acid-treated zeolite can also be further washed, if desired,with a mild acid solution such as, for example, ammonium nitrate whichis capable of maintaining the pH of the wash solution in acidic range.The volume of the acid generally can be the same volume as the acid forreducing the aluminum content in a zeolite. The mild acid treatment canbe carried out under substantially the same conditions disclosed in theacid treatment for reducing aluminum content in a zeolite. Thereafter,the resulting solid can be washed and dried as disclosed above.

The dried, acid-treated zeolite, whether it has been further washed witha mild acid or not, can be calcined, if desired, under a condition knownto those skilled in the art. Generally such a condition can include atemperature in the range of from about 250 to about 1,000, preferablyabout 350 to about 750, and most preferably 450 to 650° C. and apressure in the range of from about 0.5 to about 50, preferably about0.5 to about 30, and most preferably 0.5 to 10 atmospheres (atm) forabout 1 to about 30 hours, preferably about 2 to about 20 hours, andmost preferably 3 to 15 hours.

Thereafter, the acid-treated zeolite, whether it has been calcined ornot, can be incorporated therein, or preferably impregnated thereon anactivity promoter precursor. According to the second embodiment of thepresent invention, any activity promoter precursor which can beconverted to an activity promoter, as disclosed in the first embodimentof the invention, that, as compared to use of a zeolite or acid-treatedzeolite only, can effect the improvement of conversion of a C₉ +aromatic compound to BTX or xylene or the reduction of coke in atransalkylation process, can be employed. Presently it is preferred thatan activity promoter precursor be selected from the group consisting ofmolybdenum compounds, lanthanum compounds, phosphorus compounds, boroncompounds, magnesium compounds, tin compounds, titanium compounds,zirconium compounds, germanium compounds, indium compounds, cesiumcompounds, and combinations of two or more thereof.

Generally any lanthanum compounds which, when incorporated orimpregnated into a zeolite are effective to enhance the conversion of aC₉ + aromatic compound, can be used in the present invention. Examplesof suitable lanthanum compounds include, but are not limited to,lanthanum acetate, lanthanum carbonate, lanthanum octanoate, lanthanumfluoride, lanthanum chloride, lanthanum bromide, lanthanum iodide,lanthanum nitrate, lanthanum perchlorate, lanthanum sulfate, lanthanumtitanate, and combinations of two or more thereof.

Similarly, any molybdenum compounds which, when incorporated orimpregnated into a zeolite are effective to enhance the conversion of aC₉ + aromatic compound can be used in the present invention. Suitablemolybdenum compounds include, but are not limited to, molybdenum (II)chloride, molybdenum(III) chloride, molybdenum(II) acetate,molybdenum(IV) chloride, molybdenum(V) chloride, molybdenum(VI)fluoride, molybdenum hexacarbonyl, molybdenum sulfide, sodiummolybdates, potassium molybdates, molybdenum(VI) oxychloride,molybdenum(IV) sulfide, ammonium tetrathiomolybdate, ammonium molybdate,ammonium dimolybdate, ammonium heptamolybdate(VI), and combinations oftwo or more thereof.

Examples of the other activity promoters can be found in applicants'copending application Ser. No. 08/705,926 in which the term "acid sitemodifier" instead of activity promoter is used therein, the disclosureof which is herein incorporated by reference.

Generally, a zeolite, calcined zeolite, zeolite-binder, calcinedzeolite-binder or acid-treated zeolite, can be combined with suchactivity promoter precursor in any suitable weight ratios which wouldresult in the weight ratios of an activity promoter to a zeolitedisclosed in the first embodiment of the invention. Presently it ispreferred that such combination be carried out in a suitable liquid,preferably an aqueous medium, to form an incipient wetnesszeolite-precursor mixture or a modified zeolite.

The zeolite and the precursor are well mixed. In the next step of theprocess, the modified zeolite is subjected to calcination under acondition that can include a temperature in the range of from about 300°C. to about 1000° C., preferably about 350° C. to about 750° C., andmost preferably 400° C. to 650° C. under a pressure that can accommodatethe temperatures and is generally in the range of from about 1 to about10, preferably about 1, atmospheres for a period in the range of fromabout 1 to about 30, preferably about 1 to about 20, and most preferably1 to 15 hours. Upon completion of incorporating or impregnating theactivity promoter into the zeolite by calcination, a promoted zeolite isformed.

The composition of the invention then can be, if desired, pretreatedwith a reducing agent before being used in a hydrodealkylation or atransalkylation process. The presently preferred reducing agent is ahydrogen-containing fluid which comprises molecular hydrogen (H₂) in therange of from 1 to about 100, preferably about 5 to about 100, and mostpreferably 10 to 100 volume %. The reduction can be carried out at atemperature, in the range of from about 250° C. to about 800° C. forabout 0.1 to about 10 hours preferably about 300° C. to about 700° C.for about 0.5 to about 7 hours, and most preferably 350° C. to 650° C.for 1 to 5 hours.

According to the third embodiment of the present invention, a processcomprises, consists essentially of, or consists of contacting a fluidstream with a catalyst composition, optionally in the presence of aninert gas, preferably a hydrogen-containing fluid, under a conditionsufficient to enhance or effect the conversion of a hydrocarbon to amixture rich in C₆ to C₈ aromatic hydrocarbons wherein said fluid streamcomprises a hydrocarbon or hydrocarbon mixture which can comprise C₉ +aromatic compounds, paraffins, olefins, naphthenes. The catalystcomposition is the same as that disclosed in the first embodiment of theinvention which can be prepared by the second embodiment of theinvention.

The term "fluid" is used herein to denote gas, liquid, vapor, orcombinations thereof. The term "increase, improve, or enhance" refers toincreased BTX in the product employing the catalyst composition ascompared to employing an untreated zeolite. Examples of a hydrocarboninclude, but are not limited to, butane, isobutanes, pentane,isopentanes, hexane, isohexanes, cyclohexane, methylcyclohexane,heptane, isoheptanes, octane, isooctanes, nonanes, decanes, undecanes,dodecanes, tridecanes, tetradecanes, pentadecanes, hexadecanes, butenes,isobutene, pentenes, hexenes, 1,2,3-trimethylbenzene,1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene,1,2,4,5-tetramethylbenzene, n-propylbenzene, 3-ethyltoluene,4-ethyltoluene, 3-n-propyltoluene, 4-n-propyltoluene,1,3-diethylbenzene, naphthalenes, and combinations of any two or morethereof. In some feed fluids, such as, for example, gasoline cancomprise some benzene, toluene, ethylbenzene, and xylenes.

Any fluid which contains a C₉ + aromatic compound can be used as thefeed for the process of this invention. Generally, the fluid feed streamcan also contain olefins, naphthenes (cycloalkanes), or some aromaticcompounds. Examples of suitable, available fluid feeds include, but arenot limited to, gasolines from catalytic oil cracking processes,pyrolysis gasolines from thermal cracking of saturated hydrocarbons,naphthas, gas oils, reformates, and combinations of any two or morethereof. The origin of this fluid feed is not critical. Thoughparticular composition of a feed is not critical, a preferred fluid feedis derived from gasolines which generally contain more paraffins(alkanes) than combined content of olefins, cycloalkanes, and aromaticcompounds.

Any fluid which contains a C₉ + aromatic compound as disclosed above canalso be used as the feed for the process of this invention. A C₉ +aromatic compound can have the formula of R'_(q) Ar wherein each R' is ahydrocarbyl radical having 1 to about 15 carbon atoms and isindependently selected from the group consisting of alkyl radicals, arylradicals, alkaryl radicals, aralkyl radicals, alkenyl radicals, andcombinations of any two or more thereof, q is a whole number from 1 to5, and Ar is an aryl or arylene group. The origin of the C₉ + aromaticcompounds feed is not critical. However, a preferred fluid feed is aC₉ + aromatic compound derived from the heavies fraction of a productfrom a paraffin, in particular gasoline, aromatization reaction.Generally, this heavies fraction contains primarily trimethylbenzenessuch as 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, and1,3,5-trimethylbenzene; tetramethylbenzenes such as 1,2,3,4-tetramethylbenzene, 1,2,3,5 -tetramethylbenzene and1,2,4,5-tetramethylbenzene; and naphthalenes. Additionally,n-propylbenzene, 3-ethyltoluene, 4-ethyltoluene, 3-n-propyltoluene,4-n-propyltoluene, and 1,3-diethylbenzene can also be present in thefluid.

In a hydrodealkylation process benzene, toluene, ethylbenzene andxylenes are generally substantially absent from the fluid, i.e., theamount of each of these aromatic hydrocarbons is less than about 0.1weight % in the fluid. However, in a transalkylation process, one ormore of benzene, toluene, ethylbenzene and xylenes can be present in thefeed to effect a significant alkylation of the lower aromatichydrocarbons by the C₉ + aromatic compounds, i.e., significanttransalkylation occurs. The condition for carrying out hydrodealkylationand transalkylation can be substantially the same as disclosedhereinbelow.

Any hydrogen-containing fluid which comprises, consists essentially of,or consists of, molecular hydrogen (H₂) can be used in the process ofthis invention. This hydrogen-containing fluid can contain H₂ in therange of from about 1 to about 100, preferably about 5 to about 100, andmost preferably 10 to 100 volume %. If the H₂ content in the fluid isless than 100%, the remainder of the fluid may be any inert gas such as,for example, N₂, He, Ne, Ar, steam, or combinations of any two or morethereof, or any other fluid which does not significantly affect theprocess or the catalyst composition used therein.

The contacting of a fluid feed stream containing a hydrocarbon with ahydrogen-containing fluid in the presence of the catalyst compositioncan be carried out in any technically suitable manner, in a batch orsemicontinuous or continuous process, under a condition effective toconvert a hydrocarbon to a C₆ to C₈, aromatic hydrocarbon. Generally, afluid stream as disclosed above, preferably being in the vaporizedstate, is introduced into a suitable hydroprocessing reactor having afixed catalyst bed, or a moving catalyst bed, or a fluidized catalystbed, or combinations of any two or more thereof by any means known toone skilled in the art such as, for example, pressure, meter pump, andother similar means. Because a hydroprocessing reactor and processtherewith are well known to one skilled in the art, the description ofwhich is omitted herein for the interest of brevity. The condition ofthe process of the invention can include a weight hourly space velocityof the fluid feed stream in the range of about 0.01 to about 100,preferably about 0.05 to about 50, and most preferably 0.1 to 30 gfeed/g catalyst/hour. The hydrogen-containing fluid (gas) hourly spacevelocity generally is in the range of about 1 to about 10,000,preferably about 5 to about 7,000, and most preferably 10 to 10,000 ft³H₂ /ft³ catalyst/hour. Generally, the pressure can be in the range offrom about 10 to about 2000 psig, preferably about 100 to about 1000psig, and most preferably 200 to 750 psig, and the temperature is about250 to about 1000° C., preferably about 300 to about 750° C., and mostpreferably 400 to 650° C.

The process effluent generally contains a light gas fraction comprisinghydrogen and methane; a C₂ -C₃ fraction containing ethylene, propylene,ethane, and propane; an intermediate fraction including non-aromaticcompounds having greater than 3 carbon atoms; a BTX aromatichydrocarbons fraction (benzene, toluene, ortho-xylene, meta-xylene andpara-xylene); and a C₉ +fraction which contains aromatic compoundshaving 9 or more carbon atoms per molecule. Generally, the effluent canbe separated into these principal fractions by any known methods suchas, for example, fractionation distillation. Because the separationmethods are well known to one skilled in the art, the description ofwhich is omitted herein. The intermediate fraction can be fed to anaromatization reactor to be converted to aromatic hydrocarbons; methane,ethane, and propane can be used as fuel gas or as a feed for otherreactions such as, for example, in a thermal cracking process to produceethylene and propylene. The olefins can be recovered and furtherseparated into individual olefins by any method known to one skilled inthe art. The individual olefins can then be recovered and marketed. TheBTX fraction can be further separated into individual C₆ to C₈ aromatichydrocarbon fractions. Alternatively, the BTX fraction can furtherundergo one or more reactions either before or after separation toindividual C₆ to C₈ hydrocarbons so as to increase the content of themost desired BTX aromatic hydrocarbon. Suitable examples of suchsubsequent C₆ to C₈ aromatic hydrocarbon conversions aredisproportionation of toluene (to form benzene and xylenes),transalkylation of benzene and xylenes (to form toluene), andisomerization of meta-xylene and/or ortho-xylene to para-xylene.

After the catalyst composition has been deactivated by, for example,coke deposition or feed poisons, to an extent that the feed conversionand/or the selectivity to the desired ratios of olefins to BTX havebecome unsatisfactory, the catalyst composition can be reactivated byany means known to one skilled in the art such as, for example,calcining in air to burn off deposited coke and other carbonaceousmaterials, such as oligomers or polymers, preferably at a temperature ofabout 400 to about 1000° C. The optimal time periods of the calciningdepend generally on the types and amounts of deactivating deposits onthe catalyst composition and on the calcination temperatures. Theseoptimal time periods can easily be determined by those possessingordinary skills in the art and are omitted herein for the interest ofbrevity.

The following examples are presented to further illustrate thisinvention and are not to be construed as unduly limiting the scope ofthe present invention.

EXAMPLE I

This example illustrates the preparation of beta zeolite-containingcompositions essentially according to the second embodiment of theinvention.

Catalyst A was produced from a commercial Zeocat beta zeolite obtainedfrom CU Utikon Chemie, Utikon, Switzerland. The beta zeolite (powder; 50g) was well mixed with 50 g of CATAPAL® D alumina obtained from VistaChemical Company (Houston, Texas), and 83 g of 10 weight % acetic acidfollowed by extrusion to produce an alumina-bound zeolite in 1/16 inchextrudates. The alumina-bound zeolite was calcined at 538° C. for 6hours to produce catalyst A (alumina-bound zeolite). This was used ascontrol.

This alumina-bound zeolite (catalyst A above; 3 g) was impregnated witha solution containing 2.07 g of 6.57 weight % ammonium molybdate ((NH₄)₆Mo₇ O₂₄.4H₂ O) by incipient wetness method at about 25° C. The ammoniummolybdate-impregnated zeolite was then calcined in air (muffle furnace)for 6 hours at 538° C. to produce 2.93 g of molybdenum-promoted zeolite(catalyst B) containing 2.522 weight % molybdenum by calculation.

Catalyst C was prepared by first mixing 20 g of powder Zeocat betazeolite with 400 g of aqueous solution of 1.0 M oxalic acid at 50° C.for 16 hours to produce a solid mixture. The mixture was then washedwith running water for about 30 minutes at room temperature (about 25°C.) followed by drying at 125° C. for 16 hours to produce anacid-treated beta zeolite. The acid-treated beta zeolite was mixed with20 g of CATAPAL® D alumina and 35 g of 10 weight % acetic acid to make apaste. The paste was extruded at 25° C. to 1/16 inch extrudates whichwere then calcined at 538° C. for 6 hours to produce 26.74 g ofalumina-bound acid-treated beta zeolite. Of this 26.74 g, 3 g wasimpregnated with a solution containing 2.02 g of 6.57 weight % ammoniumheptamolybdate ((NH₄)₆ MO₇ O₂₄.4H₂ O) solution by incipient wetnessmethod followed by calcinating in air for 6 hours at about 538° C. toproduce 2.96 g Mo-promoted acid-treated zeolite containing 2.409 weight% Mo by calculation.

EXAMPLE II

This example illustrates the use of the zeolite materials (catalysts A,B, and C) described in Example I in a transalklylation of a feedcomprising C₉ + aromatic compounds and toluene to produce a productcontaining a higher concentration of BTX than the feed. The compositionof aromatic compounds, up to 12 carbons per molecule, of the feed usedfor the transalkylation is shown in Table I. There were some paraffins,isoparaffins, and naphthenes as well as numerous unidentified componentsin the feed that are not shown in Table I.

                  TABLE I                                                         ______________________________________                                        Aromatics (weight %)                                                                           C.sub.6   0.000                                                                       C.sub.7 (toluene)    50.248                                                   C.sub.8                 0.411                                                 C.sub.9                 11.315                                                C.sub.10                12.664                                                C.sub.11                9.457                                                 C.sub.12                3.001                                                 Total                  87.096                          Sulfur (ppmw)                                 658                           ______________________________________                                    

A stainless-steel reactor tube (inner diameter: 2.5 cm; length: 50 cm)was filled with a 20 ml bottom layer of Alundum® alumina (inert, lowsurface area alumina, provided by Norton Company, Worcester, Mass.), 5ml of one of the zeolite materials described in Example I, and a 20 mltop layer of Alundum®. The reactor and its content were pre-heated fromroom temperature to the desired reaction temperature of about 575° C.The zeolite-containing catalysts were pretreated with flowing hydrogengas at a rate of 260 ml per minute at 500° C. starting at 25° C. andramping at 10° C./min. The reaction pressure was set at 500 psig. Aliquid feed as shown in Table I was introduced into the heated reactorat a rate of 20 ml/hour. The product, which exited the reactor, wascooled, analyzed by means of an online gas chromatograph at intervals ofabout 1 hour. The results are also summarized in Table II.

                  TABLE II                                                        ______________________________________                                                             %                                                                      Time.sup.b  Temp           Conv         % Conv.sup.c  wt %                                                        wt %      Avg wt %                                                       Catal.sup.a  (hr)                                                            (° C.)   C.sub.9 +                                                     Naph         Xyln's                                                           Lts.sup.d  Coke/hr.sup.d          ______________________________________                                        A     7.27    505    20.5 21.3    1.96 2.1  2.72                                B           7.69       501           74.6           80.4         25.96                                                       11.7      1.83                 C           7.37       504           79.2           92.1         28.38                                                       2.6       1.63               ______________________________________                                         .sup.a See catalyst designations in Example I.                                .sup.b Time of transalkylation or hydrodealkylation reaction.                 .sup.c Conversion of naphthalenes.                                            .sup.d Light hydrocarbons having 6 or less carbona toms per molecule.         .sup.e Coke was determined at the end of the reaction by removing the         catalysts from the reactor and determined with a thermal gravimetric          analyzer (TGA), manufactured by TA Instruments, New Castle, Delaware.    

The results shown in Table II demonstrate that use of a beta zeolite ascatalyst (catalyst A) in transalkylation reaction had a low conversionof C₉ + aromatic compound. Impregnation of the zeolite with molybdenum(catalyst B) improved the conversion of C₉ + aromatic compounds toxylenes and reduced the coke rate in a transalkylation process ascompared to the control (catalyst A), but significantly increased thelow value hydrogenolysis products (lights: C₁ -C₆). Table II also showsthat an acid-treated beta zeolited impregnated with molybdenum (catalystC) had considerably higher conversion of C₉ + aromatic compounds(including naphthalenes), higher xylenes yield, and lower coking ratethan catalysts A and B.

The results shown in the above examples clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe ends and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

That which is claimed is:
 1. A process for producing a zeolitecomposition consisting essentially of (1) contacting a beta zeolite withoxalic acid to produce an acid-treated beta zeolite; (2) contacting saidacid-treated beta zeolite with a binder to provide a bound acid-treatedbeta zeolite (3) contacting said bound acid-treated beta zeolite with anactivity promoter precursor selected from the group consisting ofmolybedenum compounds thereby incorporating said activity promoterprecursor into said bound acid-treated beta zeolite to form a modifiedzeolite and (4) calcining said modified zeolite.
 2. A process accordingto claim 1 wherein said molybdenum compounds are selected from the groupconsisting of molybdenum chlorides, molybdenum acetates, molybdenumfluorides, molybdenum hexacarbonyl, molybdenum sulfides, sodiummolybdates, potassium molybdates, molybdenum oxychlorides, ammoniumtetrathiomolybdate, ammonium molybdate, ammonium dimolybdate, ammoniumheptamolybdate, and combinations of two or more thereof.
 3. A processaccording to claim 2 wherein said molybdenum compound is ammoniumheptamolybdate.
 4. A process according to claim 1 wherein the weightratio of said zeolite to said binder is in the range of from about 200:1to about 0.1:1.
 5. A processing according to claim 4 wherein saidcontacting step (1) is conducted under conditions comprising aconcentration of said beta zeolite in an oxalic acid solution in therange of from about 0.01 to about 500 grams per liter; an initial pH ofsaid oxalic acid solution adjusted to lower than about 7; a temperaturein the range of from about 30° C. to about 200° C.; a time period in therange of from about 10 minutes to about 30 hours; and a pressure in therange of from about 1 to about 10 atmospheres.
 6. A process according toclaim 5 wherein said acid-treated beta zeolite is dried and calcined. 7.A process for producing a zeolite composition consisting essentially of(1) contacting a beta zeolite with oxalic acid to produce anacid-treated beta zeolite; (2) contacting said acid-treated beta zeolitewith a binder to provide a bound acid-treated beta zeolite (3)contacting said bound acid-treated beta zeolite with an activitypromoter precursor consisting essentially of ammoniumheptamolybdatethereby incorporating said activity promoter precursor into said boundacid-treated beta zeolite to form a modified zeolite and (4) calciningsaid modified zeolite.